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added documentation for the new request_stack service #2956

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Sep 12, 2013
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added documentation for the new request_stack service #2956

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38 changes: 30 additions & 8 deletions book/service_container.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -270,14 +270,6 @@ looks up the value of each parameter and uses it in the service definition.

<argument type="string">http://symfony.com/?foo=%%s&bar=%%d</argument>

.. caution::

You may receive a
:class:`Symfony\\Component\\DependencyInjection\\Exception\\ScopeWideningInjectionException`
when passing the ``request`` service as an argument. To understand this
problem better and learn how to solve it, refer to the cookbook article
:doc:`/cookbook/service_container/scopes`.

The purpose of parameters is to feed information into services. Of course
there was nothing wrong with defining the service without using any parameters.
Parameters, however, have several advantages:
Expand Down Expand Up @@ -762,6 +754,36 @@ Injecting the dependency by the setter method just needs a change of syntax:
and "setter injection". The Symfony2 service container also supports
"property injection".

Injecting the Request
~~~~~~~~~~~~~~~~~~~~~

.. versionadded:: 2.4
The ``request_stack`` service was introduced in version 2.4.

Almost all Symfony2 built-in services behave in the same way: a single
instance is created by the container which it returns whenever you get it or
when it is injected into another service. There is one exception in a standard
Symfony2 application: the ``request`` service.

If you try to inject the ``request`` into a service, you will probably receive
a
:class:`Symfony\\Component\\DependencyInjection\\Exception\\ScopeWideningInjectionException`
exception. That's because the ``request`` can **change** during the life-time
of a container (when a sub-request is created for instance).

As of Symfony 2.4, instead of injecting the ``request`` service, you should
inject the ``request_stack`` service instead and access the Request by calling
the ``getCurrentRequest()`` method. For earlier versions, or if you want to
understand this problem better, refer to the cookbook article
:doc:`/cookbook/service_container/scopes`.

.. tip::

If you define a controller as a service then you can get the ``Request``
object without injecting the container by having it passed in as an
argument of your action method. See
:ref:`book-controller-request-argument` for details.

Making References Optional
--------------------------

Expand Down
16 changes: 7 additions & 9 deletions cookbook/service_container/scopes.rst
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Expand Up @@ -6,8 +6,13 @@ How to work with Scopes

This entry is all about scopes, a somewhat advanced topic related to the
:doc:`/book/service_container`. If you've ever gotten an error mentioning
"scopes" when creating services, or need to create a service that depends
on the ``request`` service, then this entry is for you.
"scopes" when creating services, then this entry is for you.

.. note::

If you are trying to inject the ``request`` service, the simple solution
is to inject the ``request_stack`` service instead and access the current
Request by calling the ``getCurrentRequest()`` method.

Understanding Scopes
--------------------
Expand Down Expand Up @@ -337,10 +342,3 @@ The service config for this class would look something like this:

Injecting the whole container into a service is generally not a good
idea (only inject what you need).

.. tip::

If you define a controller as a service then you can get the ``Request``
object without injecting the container by having it passed in as an
argument of your action method. See
:ref:`book-controller-request-argument` for details.